The present invention relates to a device and an associated apparatus for controlling the winding of threads, yarns and the like on rotating supports, for example, for forming reels in the textile industry. It is known that in the textile industry every process which is performed using a thread results in the need to store the thread itself so that it is available in the most convenient form for the subsequent operations. One of the most common forms used for said storage operation consists in a so-called reel or a cylindrical element onto which the thread is wound so as to produce a spool (reel) which must have well-defined characteristics—such as the diameter, weight, form, unwinding precision and speed. These parameters define the degree of suitability of a certain type of reel for the subsequent processing operation which may require a high unwinding speed, or a winding tension which is as small as possible, or a uniform density or high volume.
It is also known that such characteristics are essentially determined by the procedures and the conditions used for winding the reel, which winding operation, however, must be performed as rapidly and precisely as possible.
Such winding operation is basically performed by fastening one end of a thread to a cylinder supporting the reel and causing rotation of the cylinder itself by means of a controlled motor; the thread is at the same time inserted into a guide element (thread guide) actuated so as to perform an alternating rectilinear movement with a trajectory parallel to the axis of the cylinder.
Winding of the thread onto the reel gives rise to two main problems relating to control, namely:                the need to minimise the time for reversal of the movement of the thread guide so as to obtain the maximum possible winding speed; and        the need to ensure the maximum precision of the thread reversal point, namely the point where the thread terminates an outward winding cycle and starts the return winding cycle; control over the reversal position is of crucial importance for preventing dropping of the thread from the reel or, on the other hand, overlaying of the thread (beading)—a direct cause of breakage of the thread and/or incorrect unwinding of the reel during the subsequent processing operations.        
Both the abovementioned control-related problems are mainly influenced by the mechanical devices for driving and transmission of the movement from the actuating motor(s) to the thread-guide device: these mechanical devices introduce in fact a high degree of imprecision due to manufacturing tolerances, wear of the said devices over time (with consequent need for maintenance), and the fact that one of these elements usually consists of a drive belt which is inevitably subject to a certain degree of play which rapidly alters the mechanical characteristics thereof, resulting in an unpredictable degree of imprecision. In addition to this, the mechanical components introduce a high inertia which contrasts with the need for a high dynamic component during reversal of the movement of the thread guide.
All these factors therefore result in the need for continuous re-calibration of the apparatus in order to compensate for the operational defects associated therewith, or alternatively a thread storage quality which is below the expected standard must be accepted.
The prior art according to the preamble of claim 1 is disclosed in JP-8-217332 into which a magnet with poles aligned along the direction of displacement is associated to a guide member of the thread.